Production of sulphur



July 25, 1933. H. F. MERRIAM PRODUCTON OF SULPHUR Filed July 9. 1951 ww EN Patented July 25, 1933 UNITED siTATESA PATENTvr OFFICE HENRY E. MERRIAM, OE. WEST ORANGE, NEW4 JERSEY, yAssIeNoR"mo GENERAI'J CHEMICAL COMPANY, OE NEW YORK, NjY., A CORPORATION OE NEW YORK` PRODUCTION 0F SULPH'UR Application filedrJuly 9,

The inventionfrelates to the production of sulphur, and particularly to av process for producing elemental sulphurfronigasp mixtures containing sulphurdloxide, oxy- It has also Vbeen suggested that sulphur dioxide might vbe separated from a gas mixture by absorbing the sulphur dioxide in a suitable absorbent, as Water Or a dilute acid,` and that the sulphur 'dioxide thus absorbed might then be released from -the. absorbing' medium by the action of a ernment, or stream of air. s j '-A Y f Sulphur dioxide gas mixtures, to the treatment of which the presentinvention relates,

as a rule contain quantities of oxygen largely i in excess of the amount of sulphur dioxide.

According to prior processes `for the production'of relemental sulphur from Vsuch gases, it has been the practice to add' to these gas mixtures, reducing gases in such quantities asto provide reacting proportions of reducing and, reducible gases, Becausey of the comparatively large amount of oxygen con-z tainedfin the'gasmixtures over and above he oxygen combined with the sulphur,` itvV has been necessary, in 'order to eii'ect substantially complete reduction of the sulphur, to employ reducing agents in suflicient quantities notlonly to reduce thesulphur dioxide,

but also to combine With the free oxygen' contained in the gas mixtures. Such. processesV are wasteful of fuel or other reducing agents used for bringing about the reduc# tion of sulphur, since large kquantities of the reducing agents em'ployediact only tocombine With the freevoxygen of the gas mixeconomically than heretofore.

1931.Y` serial No. 549,632.

the actual 'reduction of sulphur dioxide.

'.It is the primary object of the present invention to provide a `process for the production of elemental sulphur from commercially obtainable gas mixtures Containing sulphur dioxide and oxygen 'vvvherebyminimum amounts oflreduc'ingagents are required to bring about reduction ofthe sulphur, so that the production of sulphur from such gas mixtures may be eected much more Another object of the invention isto provide a process whereby sulphur dioxidemay be separated c from a gasstream and obtaned'eitherin a pure-form or in admixture With reducing gases', or in any event in agas mixture conture, and thus serve no useful purpose in taining no constituents which uselesslycon'i sume reducing agents'in the subsequent reductionprocedure. In brief, the invention is directedto'a processfor thereduction of sulphur from gas mixtures containing sulphur dioxide and oxidizing gasesfin which only such quantities of reducing agents are l 'l utilized as arenecessary to efectthe reduction of the sulphur dioxide. tl, c In the, practice of the invention a gas containing sulphur dioxide, for example a), burner gas, maybe contacted with a ysuit-v able absorbing agent, such as Water, whereby the sulphur dioxide is largely absorbed and .removed from the gas stream. f Preferably,

the sulphur dioxide'is then removed fromr the absorbent by and at the same time ad# mixed with a reducing gaseous medium which is passedv incontact With the absorb`` ent. `Theresulting'mixture of sulphur dioxide andfreducing gas may, if desired, be heated through .heat exchange, and then re-` acted to vproduce elemental sulphur", preferably vin thepresence of a catalytic agent and tial gas-s mixture throughV the absorbing medinm,.such as Water, 'is preferably in ach` cordance Withthe countercurrent principle. Removal of the sulphur `dioxide 'from the 'at' anA elevated* temperature. The sulphurVV` umk 2o; phur dioxide to sulphur.

absorbing medium may be effected by passpebbles, coke, broken refractories, Raschig ing a reducing` gaseous medium therethrough preferably also countercurrently. The reducing gaseous medium employed for this purpose may be any suitable gas capable of reducing sulphur dioxide, as methane, carbon monoxide, hydrogen, either alone or in Various mixtures, as producer gas, Water gas, coal gas, natural gas, etc. Furthermore, the removal of sulphur dioxide, may be accomplished under the influence of heat whereby a more complete separation of the sulphur dioxide is effected, and the sulphur dioxide concentration of the gas mixture increased. rfhe amount of reducing gaseous medium contacted with the absorbing agent is preferably such that there will beobtained a mixture of sulphur dioxide and reducing gas in such proportions as will reduce the sule The mixture of sulphur dioxide and reducing gas may then be conducted in heat exchange relation with a heating medium, such for example asthe s reacted gaseous mixture, to a suitable converter in whichthe sulphur dioxide and reducing Vgas are reacted, preferably in the presence of a catalyst, to bring about the formation of sulphur. The reaction mixture from the converter is cooled, and the l sulphur condensed and separated from the gas. l Y

The conditions under which the reduction of sulphur dioxide lis carried out should be such that-the production of compounds of `sulphur other than elemental sulphur is lreduced toa minimum. The constituents of the original gaseous mixture other than sul- Y phur dioxide are largely separated from the sulphur dioxide in the absorption step, and `a'rsubstantialiy pure sulphur dioxide is thus obtained. 'The inert gases accompanying the reducing gas used for removing sulphur dioxide from the absorbing medium passV from the sulphur separator or collector and A may be permitted eitherto dissipate in the 'atmosphere or may be used as a diluting means for reducing the gaseous medium in order to adjust the quantity of reducing agent to `that required to effect efiicient reduction of the sulphur dioxide. Other inert gases, of course, may be used as diluents.

YFor a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawing in which there is illusrings, etc. for the purpose of providing an extended surface of contact between an ascending gaseous stream and a descending absorbent. In the upper part of the absorber there is positioned a perforated plate 5 for distributing the absorbent and leading to the space above the plate is a pipe 6 rfor the introduction of absorbent through the action of a pumpV 7. The absorber -2 is pro- Avided also with an exit pipe 8 having a valve 39 positioned near the top beneath the plate 5 and-a liquid outlet 9 at the base and beneath the lower perforated plate 3. Connected Awith the pipe 9 is a receiver 10 which is connected with a pump 12 by a pipe 11.

A conduit 13 leads from the pump 12 to a stripper 14 withl which it connects at the top and above a distributing plate 15. Within the stripper 14 is a lower perforated plate 16 supporting 4a filling material 17.

The material vcollecting in the bottom of` thel stripper 14 is led away by a pipe 18 to a receiver 19 from which it maybe conducted to the pump 7 by a conduit 20. e

The introduction of a reducing gaseous medium is effected through a pipe 22 having a valve 38 and a conduit 21 which opensy into thebase of the stripper 14 beneath vthe perforated'plate 16. From the stripper 14, a pipe 23 connects with a blower 24, and the blower in turn by a pipe 25 with a heat exchanger26. A 'conduit 27 connects the heat exchangerwith'a converter 28.l In order to accomplish heat exchange, the converter is connected by a pi e 29 with the heat exchanger, and there rom a pipe 3() leadsto a cooler 31 whichis connected Aby a conduit 32 with the collector 33. The collector is provided with anoutlet 34 controlled by a valve 40. From the outlet 34, a v`conduit 35, having aV valve 41, leads to the reducing gas inlet 22. An absorbent inlet 36 provided with a valve 37, isconnected to the top olf the absorber 2 for the introduction of liquid above the distributing o r perforatedplate 5.Y The.

receivers 10 and 19 have outlets 44 and 42 respectively, which outlets may be closed by the valves 45 and 43, respectively.

As an illustrativev embodiment of al manner in which the inventionl may be carried out in practice, the following yexample is given:

A 'gas mixture containing sulphur dioxide and oxygen, which may be obtained from a smelter or sulphide roaster, may be introduced by the inlet vlbeneath the lower per-` forated plate 3 of the absorber 2, and contacte'd therein with a suitable absorbing liquid, as water, or `dilute acid introduced either through the pipe 6 or the pipe 36 and being distributed over the filling materiall within the converter by the distributing plate 5. Contacting of the sulphur dioxide gas with the absorbing liquid on the couna blower, and is forced through the heat exchanger in which the gaseous mixture is tei-current principle effects the solution'of the sulphur dioxideivhile permitting the insoluble gaseous constituents, particularly the excess oxygen, nitrogen, etc.v to pass there-V through, andfromthe absorber by the exit gas outlet 8. The absorbing liquid holding the sulphur dioxide in solution collectsA beneath the lower plate 3, and is "conducted to the receiver l() by the pipe 9. f

N From the receiver the Vsulphur dioxide solutionis forced to the top of the stripper 14 by means of the pipe 1l, pump l2 and pipe 13, and is introduced thereinto near the top and `above the distributing plate 15. The solution passes` down through the stripper over the filling material and is contacted during its descent with a reducing gaseous medium which may becoal gas, prof duc'er4 gas, natural gas,`etc., whereby the Vsulphur dioxide content isremoved. The

stripped absorbent `flows from Vthe stripper by the passage 18 into receiver 19 from which, bythe pipe 20, it is conducted to the pump 7 and, from thence to absorber 2, thus completing the circuit and permitting i'euse of the-absorbent. removal of the sulphur dioxide in the stripper 14 may be facilitated and a larger proportion of the sulphur dioxide driven out 4of the absorbent by conducting the 'stripping operation under the influence of If desired, the release or heat, forv example, by raising the tempera,- ture of the saturated solution 15 to 25 C.

whereby the sulphur dioxide concentration. .of the resulting gas mixturemay be in. creased.

Since the sulphur dioxide concentration is increased by heating, the `volume ofthe gases is cut vdown thus reducing the size of the apparatus involved and the plant investment. For example, Where the original burner gas contains say 8% sulphur dioxide, by heating the saturated solution, the concentration of the gas from the Astripper may be raised to l2-l5% sulphur dioxide.

.Theheating of the stripper may be accomplislied by anysuitable means notlshown or the increased temperature in the solution may be brought about by heatingthe absorbing liquid prior to the admission of the .same into the stripper.

`The passage of the reducing gaseous medium through the stripper occasions the formation of a mixture of sulphur dioxide and reducing gas, the reducing gas being admitted in the proportions which are suitable to effect a completereduction of the sulphur dioxide to sulphurin a succeeding stage of the operation. The mixture of sulphur dioxide and reducing gas passes from the stripper through pipe 23 connected with heated by heat transfer with the hot reacn tion mixture. The heated gases are then led by the pipe 27V to the converter 28 in which "the composition of the gases.

reaction betweenthe Vsulphur dioxidewand the reducing gas takes place with the formation of elemental sulphur. vThe action be# tween the sulphur dioxide and reducing gas may be` brought about either under the iniuence ofV a high temperature or in the pres-l -ence of al -suitable catalyst, such as dehydratedbauxite under proper conditionsef temperature and pressure. The temperature at which the reaction between the sulphur dioxide and reducing gases takes place depends on the nature of the catalyst and.`

, `The hot reaction gases pass Vfrom, the converter to the Vheat exchanger by the pipe 29 and from thence by a conduit 30 to the gas` cooler 3l in which coolingfof the reaction Y content of 'reducing gas ,in the reducingv gaseous medium by conducting part of the exit gas backto the ypipe 21 by means' of the valved conduit 35. e v .i

n starting the operation, `the liquidiabsorbent may be introduced through the valved inlet 36 to the absorber 2, and this ment of such absorbent as may be lost during the operation of the process. Further, y if desired, the absorber may be Aoperated at a temperature below normal temperature, as at a temperature of aboutA 15 C., valthough absorption at normal temperatures, i. e. around 20o C. is generally contemplated. In the foregoingv procedure, theamount of absorbing liquid,l for example, may be con* trolled in such a manner as to obtain the desired absorption of the sulphur dioxide.` The absorption preferably is made as coni-V plete as possible and the absorbing liquid is utilized in an amount at least sufficient to absorb substantially all of the sulphur dioxide "present in the burner gas.

Instead of absorbing theA sulphur dioxide in a liquid absorbing medium such as water or dilute acid, solid adsorbents such as silica gel may be employed. YVhen solid 'adsorbents are utilized, the adsorbed sulphur dioxide is released therefrom in anysuitable manner, for example by heating the adsorbent or by stripping by means of the `reducingl gas. lWhatevei' absorbing or `jadsorbingA mediumfis employed, the` oxygen present in the original gas-mixture together with the gaseous impurities are eliminated, with the result that they fuel consumed perunit of v I inlet may also be used to effect,replaceiwf.

CII.

`produced will be retained therein, for ex-` ample, above about 300o C;

V-occasioning undesirable side reactions.

sulphur produced is materially reduced, and the sulphur of the sulphur ydioxide is ultimately recovered in a pure form.

The converter or chamber in which the sulphur dioxide and reducing gas are reacted may be, and preferably is maintained at a temperatureabove that at which the sulphur The relative proportions of sulphur dioxide and lreducing gas should be in amounts Vapproximating the proportions required for reaction thereof to yproduce sulphur. The proper temperature of the gases for introduction into the converter or reacting chamber may, as shown above, be secured by preheating the gases ina suitable heat exchanger where they are brought in indirect heat exchanger relation with the hot gases passing lfromA the converter.

Reaction between the sulphur dioxide and reducing gas may -be effected withoutl a catalytic agent, but the action is facilitated by the employment of asuitable catalyst.

f vAs a catalyst, utilization may be made of dehydrated bauxite which is a natural mixture' of hydrated alumina, iron oxide, titanium oxide, etc., or use maybe made oi iron oxide, pyrites cinder, titaniuin-oxide, aluminum oxide, calcium sulphate, calcium` sulphide, and others. The temperature of the reacting` chamber should be maintained -so as to occasion reaction between the sulphur dioxide and the reducing gas without -teraction of the sulphur dioxide With Athe reducing gases in the converter, or reaction chamber is considered to take place, by way of illustration7 according to the following equations y 2Go sozzaoo2 s CH.l -t QSG CO2 Jr QHO -lr 2S sul so2 s enzo The reaction mixture arising in the converter is passed through a suitable heat exchange apparatus for heat transfer to the incoming gases and then through a cooler 'to reduce the temperature of the gases for subsequent deposition of the sulphur in the collector. he collector may be of a mechanical type such as a baiiie chamber with "lixed or rotating baiiles or the sulphur may be separated or precipitated electrostatically. Further, the collector' maybe of a washer type in which thesulphur is dissolved, for example in a suitable oil, or washed out with vwater or adsorbed in a suitable adsorbent, as

i to the process.

'result in the interaction of practically all of be desirable to provide for the removal of any hydrogen sulphide or sulphur dioxide in the exit gas by passing these gases through a suitable adsorber, thereby preventing'their escape. The Vabsorbed gases may be subsequently recovered and returned he production of sulphur according to the foregoing procedure may be accomplished commercially With a substantially complete utilization of the entirel sulphur dioxide content of the burner gases and may be readily and economically carried out. The invention provides a process by which the impurities present in theoriginal burner gases are eliminated and only av pure sulphur dioxide reacted with the reducingl gas, which in turn, yields a pure sulphur. The important advantage is yobtained that the oxygen content of the gases -treated is removed, which results in a material reduction in the consumption of fuel per pound of sulphur obtained. Further the concen-` tration of the sulphur dioxide gases may volume of gases passing through the systemV or apparatus. y

The invention. is not limited to the production of elemental sulphur, as Yfor example, the principles of the invention may also be utilized for the production of hydrogen sulphide. The latter sulphur compound may be formed by employing any one of the aforementioned hydrogen-containing reducing agents in sufficient quantities to continue the reduction oi the sulphur dioxide to hydrogen sulphide. A

Since certain changes may be made in carrying out the above process without departing from the scope of 'the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

iVhere the sulphur dioxide is separated from the initial gas mixture by a liquid such as water or by a solid such as ysilica gel, it is believed that-the phenomena involved are of. absorption and adsorption respectively. Vhatev'er the case may be, and

whatever substance may be employed to separate the sulphurdioxide from the other constituents of the initial gas mixture, in

the appended claims the term absorbing,

is intended to include both phenomena.

I claim:

l. A process for the production of sulphur gaseous medium .and reacting the sulphur dioxideand reducing gas in the vpresence of a catalyst to form sulphur.

A process for theproduction of sulphur Which vcomprises contacting a gas containing sulphur' dioxide With a liquid absorbing agent, removing sulphur dioxide from the absorbing agent by passing a reducing gaseous medium therethrough' under the influence of heat, and reacting the sulphur dioxide and reducing gas in the presence ofa catalyst to `form sulphur, V

4. Vrlhe process for treatinggases Which comprises contacting a gas containing sulphur dioxide with an absorbing agent, removing sulphur dioxide from the absorbing agent by means of a reducing gaseous medium, and reacting the sulphur dioxide and the reducing gas. l

5. The process-for treating gases Which comprises contactingV a gascontaining sulphiirY dioxide with an absorbingagent, re-

moving sulphur dioxide from the absorbing agentby means of natural gas and reacting the.su lphur dioxide and natural gas in the presence of a catalyst. .v l Y v 6. A process for the production of sulphur which comprises contacting `a gas containing sulphur dioxidewith Water, removing sulphur dioxide 'from the Wateifsolutionfby means of a reducing gaseous medium, andV reacting sulphur dioxide and reducinggas inthe presence of a catalyst to form sulphunf v7. A'process orthe `production of sulphur Whichcomprises contacting a gas containing sulphur dioxide with Water in Acountercur` rent flow, removing sulphur dioxide from:

the Water solution by, means Qfja reducinggaseous medium, and reacting sulphur-'dioxide and reducingigas inthe presence of aA catalyst to form. sulphur. p 8. Aprocess for the production of sulphur which comprises contacting a gascontaining` sulphur dioxide with Water in countercur# Y rent How at a temperature of about 20o C.,

, removing sulphur dioxide from the jvvater y lyst to form sulphur and separating the sul` D i sulphurl from a gas containing sulphur di-y ,551 oxide, the improvement Whichcornprises resolution formed by passing'produccr gas therethrough countercurrently under-,the inluence of heat, reacting the sulphur dioxide and producer gas in the presence of a lcataphur by cooling.

9. A processfor the production'of sulphur M which comprises contacting burner `gas con' taining sulphur dioxide With Water,,removf ing sulphur dioxide from the Water solution formed-by means of a reducing gaseous med iuin, reacting the sulphur dioxide and `reducin g gas lin the presence of a catalysttovforin sulphur, and separating the sulphur.v l0. A process for tiie productionofV sul` phur which ycomprises contacting burner gas containing `to l2' per cent. sulphur@ dioxide 'With-vater naty a temperature ol about 20 C., -removing sulphur?*dioxide frointlie 'atei' soiution thus formed` by passing producer gas therethrough `While maintainingV the` 'temperature of the solution upwards of about reacting the sulphur' `dioxide and producer in. the presence ot a catalystto yforni sulphur and separating the sulphur .from the residualgas.

11.*A process for theproductionoi sulphur which comprises contacting burner gas containing 5 toy l2` per cent; sulphur' dioxide With. Water.V at' a .temperature oi about 20 C. count-erenrrently,Y removing sulphur dioxide from the'Water,solution thus formed by passing pro-ili'icei" f a@ L. through countercurrentiy While inf ing the temperature of the solution u pivnr' j of about C., heating gaseous V mixture, reacting the sulphury dioxide and pro.`

ducerv gas in the prcseiicevof arcatalyst to form sulphur rand- V sepaiating.the fsulpliiur from the residual {i} s byfcooliiig.

12. A process' for lill:

. l b phur dioxide from the gaseousv medium', andi'cacting tliofsulpliur c the pijoductioiifol' sulphui which compi es contacting agas c oiitaining sulphur dioxide with air absor ino" agent,'removing siabsorbing Aagent by means oi reducing n a process foi-the production of sul'- v.

phur from a kgas containing sulphurl dioxide,

the improvomentV which comprises i'ei'noving sulphur dio" 'tron'iyz'in absorbi. by` means.A re 'Icing gaseous in; l and Y reacting thev ksu L duciiig gasto .fornisulphur.

I ll. `In a process-for the produetipn sulphur from `a containing sulphur.di`

oxide, the improvement which comprises ref moving sulphur dioxide from' an absorbing agentby inea-ns of a reducing` .gaseous/me# d iuin andl reacting-'the sulphur dioxide and reducing gasinthe presen'ceota catalyst yto ormsulphur.

- 15. VIn a `process for *the production of sulphur from avgas containing 'sulphur dioxide, the` improvement Wltich "comprises removing sulphur dioxide from an absorb?V ing agent by means ofja' reducing'. gaseous medium. 4

16. In a process for ythevproduction. of

ageii' um nhui' dioxide and removing sulphur dioxide from an absorbing liquid by contacting producer gas therewith Y countercurrently.

ence of a catalyst to form sulphur and separating the sulphur by cooling.

eous impurities which comprises contacting 19.*Ai process for the production of sulphur which comprises contacting burner gas containing 5 to l2 per cent. sulphur dioxide with,y Water at a temperature of about 2OQ C. countercurrently, removing sulphur dioxide from the Water solution thus formed bypassing natural therethrough countercurrently- While maintaining the temperature of the solution upwards of about 35 C., heating the gaseous mixture,

reacting the sulphur dioxide and naturalv gas in the presence of a Acatalyst to form sulphur and separating the sulphur vfrom the residual gasby cooling.

20. The processfor treating gases which comprises contacting a gas containing sulphur dioxide With a liquid absorbing` agent, removing sulphur dioxidetrom the absorbfh ing agent by means of a reducing gaseous medium, and reacting the sulphur dioxide and the reducing gas. o f n 2l. The process forv the reductionrot sulphur dioxide of a gas mixture containing' sulphurr dioxide, anfoxidizing gas and vrgasthey gas mixture With Aan absorbing agent whereby the sulphur dioxide is absorbed and separated from" the oxidizing gas andthe gaseous impurities, separating sulphur dioxide from the absorbing agent in the absence oi an oxidizing gas, andV then reacting the'sulphur dioxide and a reducing agent.

22. The process for the production of an oxygen-free sulphur dioxide gas mixture from a gas mixture containing sulphur dioxide and oxygen which comprises contactagent by means of an'oxygen-free gaseous medium. y

23. The method of treating gases contain'- ing sulphur dioxide and oxygen which comprises contactingvthe gases With an yabsorbing agent whereby the sulphur dioxide is absorbed and separated from the oxygen, andY then removing sulphur dioxide from the ab-V sorbing agent by flowing through the absorbing agent an oxygen-tree fluid 'medium Whereby'sulphur dioxide is separated from the absorbing agent and a fluid oxygen-free sulphur dioxide mixture is obtained. i

24. In the process for rthe reduction of sul'- pliur dioxide involving stripping of sulphur dioxide lfrom a sulphur dioxideabsorbent containing the same Withreducing gaseous medium, and then reacting the sulphur dioxide and reducing medium, thev improvement which comprises effecting-stripping With the reducing medium` in the presence of inert 25. In the process for the reduction of sulphur dioxide involving stripping' sulphur dioxide from a sulphur rdioxide ab# sorbent containing the` same with reducing gaseous medium, reacting the sulphur dioxide and reducingl medium, and separating sulphur reaction products from inert tail gases in the reaction gas mixture, the improvement which comprises dilutingreducing medium in the stripping Zone With inert tail gases. n

26. In the process for the reduction of sulphur dioxide involving stripping sulphur dioxide from a sulphur dioxide absorbent containing the same With gas containing V reducing inedium,`reacting the' sulphur dioxgases of the reaetionjgas mixture, the'y im-` ioo provement which comprises adinixing With c Y the reducing medium entering the stripping i' gases of the stripping zone substantially reacting proportions of sulphur dioxider and reducing medium. y c HENRY F. MERRIAM.

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